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A&P Lect.

Chapter 4 Genetics and Cellular Function

Mendelian genetics correlation between chromosome behavior and the laws of heredity
deoxyribonucleic acid (DNA) a long threadlike molecule with uniform diameter but varied length
total length of DNA 2 meters
how many molecules in nucleus of most human cells 46
genes genetic instructions for synthesis of proteins
gene segment of DNA that codes for specific protein
genome all the genes of one person; all the DNA in one 23 chromosome set
genes are... turned on and off from day to to day, hour to hour
are the products of genes always needed? no
can genes be permanently turned off? yes
example of when genes can be turned off genes for hemoglobin or digestive enzymes
gene expression DNA (transcription) ->RNA (translation-> protein
homo sapiens have ... previously believed fewer genes than the 100,000
genes generate.. millions of different proteins
genes average.. about 3,000 bases long
all humans are atleast.. 99.99% genetically identical
we now know the locations of ... 1400 disease producing mutations
genomic medicine new branch of medical diagnosis and treatment
sister chromatid 2 parallel filaments of identical DNA (within each chromosome)
final compaction enables 2 sister chromatids to be pulled apart and carried to separate daughter cells without damage to DNA
centromere where chromasomes
nucleotide consists of a sugar, a phosphate group, and a single- or double-ringed nitrogenous base
base C and T cytosine & thymine have single carbon nitrogen ring and classified as pyrimidines
base A and G Adenine & guanine have double carbon nitrogen rings and classified as purines
discovered double helix James Watson and Francis Crick
what happened in the disocvery of double helix DNA Rosalin Franklin and Maurice Wilkin were working on x-ray photographs that Wilkins ended up showing Watson and Crick and they won recognition but nobel prize was shared between the three minue Franklin because she had dies, probably due to the xrays
how many nucleotide pairs in a human genome? 3.1 billion
describe structure of chromosomes there are 46 human chromosomes that come in 2 sets of 23. one set from each parent. each pair of chromosomes has same genes but different alleles
chromatin proteins to form a fine filamentous material
DNA replication vefore a cell divides it duplicates its DNA so it can give a complete copy of all its genes to each daughter cell
kintochore protein plaques on either side of the centromere
cell cycle cell's life cycle that extends from one division to the next ; G1,S, G2,M,Cytokinesis
G1 phase the first gap phase: interval between cell division and DNA replication, accumulates materials needed to replicate DNA
S Phase synthesis phase: DNA replication occurs
G2 Phase second gap phase interval between DNA replication and cell division, synthesizes enzymes that control cell division, repairs DNA replication errors
M Phase miotic phase: cell replicates its nucleus
interphase collection of G1 S and G2 phases
G0 (zero) cells that have left the cycle for a "rest"- muscle, nerve cells
mitosis cell division in all body cells except the eggs and sperm
functions of mitosis -development of the individual from one fertilized egg to some 40 trillion cells -growth of all tissues and organs after birth -replacement of cells that die -repair of damaged tissues
4 phases of mitosis prophase, metaphase, anaphase, telophase
cytokinesis the division of cytoplasm into 2 cells telophase is the end of the nuclear division but overlaps cytokenesis pinches in 2 to form new daughehter cells creates cleavage furrow around the equator of cell
how is cytokinesis achieved -achieved by motor protein myosin pulling on microfilaments of actin in the terminal web of cytoskeleton
when do cells divide when they have enough cytoplasm for 2 daughter cells -they have replicated their DNA -they have adequate supply of nutrients -they are stimulated by growth factor -when neighboring cells die, opening up space in a tissue to be occupied by new cells
growth factor signals secreted by blood platelets, kidney cells, and other sources
when do cells stop dividing - when nutrients or growth factors are withdrawn -when they snugly contact neighboring cells -when they undergo contact inhibition
contact inhibition the cessation of cell division in response to contact with other cells
Meiosis -cell division in eggs and sperm
heredity transmission of genetic characteristics from parent to offspring
karyotype chart of 46 chromosomes laid out in order by size and other physical features
homologous chromosomes 23 pairs: the 2 members of each pairs
autosomes 22 pairs that look and carry versions of the same genes
chromosomes in homologous chromosomes 1 chromosome from each pair inherited from each parent
sex chromosomes X & Y
female chromosome homologous pair of X chromosomes
male chromosome has 1 X and one much smaller Y chromosome
diploid any cell with 23 pairs of chromosomes (somatic cells)
haploid contain half as many chromosomes as somatic cells: sperm and egg cells (germ cells)
fertilization restores diploid number to the fertilized egg and the somatic cells arise from its
locus the location of a particular gene on a chromosome
alleles different forms of gene at same locus on 2 homologous chromosomes
dominant alleleous (represented by capital letter) -corresponding trait is usually detectable in the individual -masks the effect of any recessive allele that may be present -produces protein responsible for visible trait
recessive allele (represented by lower case) -expressed only when present on both of the homologous chromosomes - no dominant alleles at that locus
genotype the alleles that an individual possesses for a particular trait
homozygous alleles 2 identical alleles for a trait
heterozygous alleles different alleles for that gene are also carriers for hereditary diseases such as cystic fibrosis
phenotype an observable trait
expressed allele an allele is expressed if it shows in the phenotype of an individual
punnet square shows how 2 heterozygous parents with cleft chins have child with uncleft chin
gene pool collective genetic makeup of population as a whole
multiple alleles more than 2 allelic forms of a trait -100 alleles are responsible for cystic fibrosis -3 alleles for ABO blood types
codominant bot alleles are equally dominant -type AB blood -both are phentypically expressed
incomplete dominance phenotype intermediate between traits each allele would have produced alone
polygenic inheritance genes at 2 or more loci, or even chromosomes,contribute to a single phenotypic trait such as skin and eye color, alcoholism, mental illness, cancer, and heart disease
pleiotropy one gene produces multiple phenotypic effects
alkaptonuria mutation on chromosome 3 that blocks the breakdown of tyrosine
sickle cell disease example of pleiotropy
sex linked traits carried on the X and Y chromosomes and therefore tend to be inherited by one sex more than the other recessive color blindness allele on X, no gene locus for that trait on Y, so red-green color blindness more common in men (mother is the carrier)
mutations changes in DNA structure due to replication errors or environmental factors (radiation, viruses, chemicals)
mutations: good/bad some mutations cause no illness effects others kill the cell, turn it cancerous, or cause genetic defects in future generations
benign tumor slow growth; contained in fibrous capsule; will not metastasize; usually easy to treat
malignant tumor called cancer; fast growing metastize
metastisize give off cells that seed the growth of multiple tumors elsewhere
oncology medical specialty that deals with both benign and maligant tumors
tumor angiognesis in-growth of blood vessels stimulated by energy-hungry tumors
how are cancers named for tissue of origin
cancer names carcinomas: in epithelial tissue lymphomas: in lymph nodes melanomas: in pigment cells of dermis (melanicytes) leukemias: in blood-forming tissues sacromas: in bone, other connective tissue, or muscle
carcinogens environmental cancer-causing agents that trigger gene mutations
what are some carcinogens radiation: ultraviolet rays, Xrays chemical: cigarette tar, food preservatives, industrial chemicals viruses: human papilomavirus, hepatitis c, type 2 herpes simplex
cancers hereditary? only 5-10%
oncogenes cause cell division to accelerate out of control -excessive production of growth factors that stimulate mitosis - the production of excessive growth-factor receptors
tumor-suppressor genes inhibit development of cancer -oppose action of oncogenes -some trigger DNA-repair enzymes
effects of cancer -replace functional tissue in vital organs -steal nutrients from the rest of the body -weaken ones immunity -open the door for opportunistic infections -often invade blood vessels, lung tissue, or brain tissue
cachexia sever wasting away of depleted tissues
mitosis nuclear division; cell division of somatic cells
prophase chromosomes condense and nuclear envelope breaks down. spindle fibers grow from centrioles. centrioles migrate to opposite poles of cell
metaphase chromosomes lie along midline of cell. some spindle fibers attach to kinetochores. fibers of aster attach to plasma membrane
anaphase centromeres divide in two. spindle fibers pull sister chromatids to opposite poles of cell. each pole now has an identical set of genes
telophase chromosomes gather at each pole of cell. Chromatin decondenses. new nuclear envelope appeaars at each pole, new nucleoli appear in each nucleus. mitotic spindle vanishes
Created by: sg109